PRCI Report 216

L51722e

Battelle Memorial Institute

(e-book version)Need: With the advancing age of the pipeline infrastructure and the competitive marketplace, cost-effective maintenance and rehabilitation is increasingly more important. Accepted methods for evaluating the remaining strength of corroded pipe, while sound and well validated, are empirical in nature and limited to specific classes of corrosion defects. The classical empirical approach, implemented into the ASME B31G "Manual for Determining the Remaining Strength of Corroded Pipelines" was the first "approved" method. PRCI then funded, developed and coordinated the approval by the US DOT of a less conservative method, RSTRENG resulting in improved economics of pipeline repair and rehabilitation. Both of these methods, however, only consider length and depth of the defect and internal pressure loading. In some regions of a pipeline, i.e. mountains and regions of unstable soil, high longitudinal or secondary axial stresses can exist. In these regions, the width of a corrosion defect can limit the pressure capacity of a corrosion defect. The limitations of the empirical models led the pipeline industry to recognize the need for improved understanding and models of the behavior of corroded areas in pipelines subjected to secondary loading.

Benefit: PCORR results in more comprehensive analysis of corroded pipe thus resulting in improved safety and performance. The PCORR results are even less conservative than B31G or RSTRENG resulting in improved economics of pipeline repair and rehabilitation. The PCORR software is applicable to existing pipelines using commonly available pipeline data. The model is simple in its input and use. This special-purpose shell finite-element model for analysis of pipeline corrosion defects can be used on standard PC's 386/486 class of IBM PC or higher.

Result: The result of this research was the development of an analytical methodology for evaluating corrosion defects under combined internal pressure and axial loads. The research investigation resulted in a broadly based program incorporating full-scale experiments, finite element investigations, and the development of fundamental mathematical and computer models. A comprehensive mathematical "model" in the form of a software program called PCORR was developed to calculate the safe pipeline operational limits under combined internal pressure and axial loads. A secondary result was the extension of this methodology to evaluate the interaction of adjacent defects, an area where the empirical models were not applicable.

Product Details

Published:

02/01/1995

Number of Pages:

100

File Size:

1 file , 2.5 MB